Polymer blends



United States Patent Office 3,522,330 Patented July 28, 1970 Int. Cl.C08f 37/18 US. Cl. 260-889 4 Claims ABSTRACT OF THE DISCLOSURE Theinvention comprises blends of 1) from about 5 to 200 parts of anethylene/vinylchloride copolymer containing about to 80% ethylene and(2) about 100 parts of polystyrene or butadiene/styrene rubber.

This application is a divisional of application Ser. No. 392,912, filedAug. 28, 1964, now US. Pat. 3,390,208.

The present invention concerns blends of vinyl chlorideethylenecopolymers with other polymeric materials.

Polystyrene has long been known as a commercial plastic having a widevariety of important properties. However, one of the objectionablefeatures of polystyrene is the flammability of this plastic. Anotherphysical property of polystyrene in which improvement is desired isimpact resistance. The major drawback of polystyrene has been its lowheat distortion temperature.

Polypropylene is a commercial plastic of increasing importance. It isexpected to supplant polyethylene in a number of commercialapplications. In comparison to high density polyethylene, polypropylenehas better heat resistance, high tensile strength, better resistance tochemicals and solvents, and greater stiffness and hardness. However, itsimpact strength is usually lower and it becomes brittle at highertemperatures than does polyethylene. It is less resistant to oxidationthan is polyethylene.

Polyethylene has been found to have rather poor resistance to sunlight,lowoxygen resistance, and a tendency to stress-crack particularly whenin contact with aqueous media. In addition, the impact resistance ofpolyethylene renders it unsuitable for some commercial applications.

In addition to the foregoing undesirable features the above mentionedplastics all suffer from the disadvantage of being flammable. Variousadditives and blending agents have been incorporated in these plasticsto decrease or modify their flammability. However, such agents areusually expensive and cause the plastic material to have otherundesirable properties.

Certain of the commercial rubber products, e.g. SBR, Butyl rubber andEPR (ethylene-propylene copolymer rubber) do not have sufiicient heatresistance, abrasion resistance, oil resistance, and non-flammability torender them suitable for certain commercial applications.

It is an object of this invention to provide a plastic material composedof a blend of polystyrene and vinyl chloride-ethylene copolymer, whichmaterial has an improved impact resistance and low flammability.

It is a further object of this invention to provide a plastic materialcomposed of a blend of polypropylene and a vinyl chloride-ethylenecopolymer, which material has improved impact strength and lowflammability.

It is also an object of this invention to provide a plastic materialcomposed of a blend of polyethylene and a vinyl chloride-ethylenecopolymer, which material has improved resistance to oxygen permeation,stress-cracking, has high impact strength, and has low flammability.

It is a still further object of this invention to provide rubbercompositions composed of a blend of synthetic rubber and a vinylchloride-ethylene copolymer. These rubber compositions have improvedheat, abrasion, oil, and flame resistance.

In accordance with the present invention, it has been found that thephysical properties of polystyrene, polypropylene, polyethylene, andrubber materials may be substantially improved by blending each of theforegoing materials with a vinyl chloride-ethylene copolymer containingfrom about 10 to about percent weight ethylene.

The vinyl chloride-ethylene copolymers that are useful in preparing theblends of the present invention may be prepared using a number ofdifferent polymerization techniques and catalysts. A particularlysuitable vinyl chlorideethylene copolymer can be made of polymerizingvinyl chloride and ethylene in the presence of a catalyst which is theproduct of a reaction of an organoborane with either molecular oxygen orperoxides. The polymerization is preferably carried out at a temperaturein the range of from about 25 C. to about 10 C. and at a pressure fromabout 500 to about 50,000 p.s.i. The preferred vinyl chloride-ethylenecopolymer produced using the foregoing catalyst should have an inherentviscosity of about 0.9. Such a copolymer has been found to impart thedesirable characteristics to the other polymeric material in the blend.Procedures for preparation of suitable vinyl chloride-ethylenecopolymers made with an organoborane-oxygen catalyst are set forth incopending US. patent applications Ser. No. 235,545; filed Nov. 5, 1962,for Copolymer Compositions now abandoned, and Ser. No. 251,071; filed Jan. 14, 1963, for Elastomeric Compositions, now abandoned, whichapplications are assigned to the same assignee as the presentapplication.

The vinyl chloride-ethylene copolymer may also be produced using adifferent type of free radical catalyst system. An alternate catalystsystem can be prepared from a mixture of (a) an oil soluble derivativeof a transion metal in an oxidation state which is capable of reducing aperoxide linkage to produce free radicals, and (b) a water insoluble butoil soluble peroxide compound. The

preferred transition metal compounds is selected from salts ofcarboxylic acid and the preferred peroxide compound is an alkyl peroxideor hydroperoxide. However, acyl peroxides, aryl peroxides, and aralkylhydroperoxides are also suitable for use. A procedure for thepreparation of suitable vinyl chloride-ethylene copolymers made with thetransition metal compound-peroxide catalyst system is set forth incopending U.S. patent application Ser. No. 340,801; filed Jan. 28, 1964,for Copolymerization Process, now abandoned, which application isassigned to the same assignee as the present invention.

The vinyl chloride-ethylene copolymers most suited for use in preparingthe blends of the present invention are those copolymers containing fromabout 10 to about 80 percent weight ethylene. A more preferredcomposition for the vinyl chloride-ethylene copolymers is from about 10to about 40 percent weight ethylene. The copolymers containing higherpercentages of vinyl chloride have been found to impart higher degreesof flame resistance to the polymer blends of the present invention.However, it has been found that when the copolymers of vinyl chlorideand ethylene contain less than about 5 percent weight ethylene they arenot fully compatible with the polymeric materials used in preparing theblends of the present invention. To provide the necessary compatibilitybetween the vinyl chloride-ethylene copolymer and the polymers used inpreparing the blends, one should utilize a copolymer having greater thanabout 5 percent weight ethylene in the copolymer.

The relative proportions of vinyl chloride-ethylene copolymer andpolymer material used in preparing the blends of the present inventionmay vary over a wide proportion,

depending upon the physical properties desired in the final blend. Ingeneral, from about to about 200 parts of the vinyl chloride-ethylenecopolymer may be utilized per 100 parts of the particular polymers. Amore preferred range is from about 5 to about 100 parts of the vinylchlorideethylene copolymer per 100 parts of the polymer. A still morepreferred composition range is one utilizing from about 5 to about 60parts of vinyl chloride-ethylene copolymer per 100 parts of polymer whenthe vinyl chlorideethylene copolymer contains about 20 percent ethylene.Another preferred range is from about to about 80 parts of vinylchloride-ethylene copolymer to about 100 parts of polymer when the vinylchloride-ethylene copolymer contains about 60 percent ethylene, all ofthe foregoing parts and percentages being by weight.

The polymeric blends of the present invention may be prepared using anysuitable mechanical blending apparatus. Banbury mixers or other standardcommercial mixing devices may be used to mill the vinylchloride-ethylene copolymer with the other polymeric component. Themechanically blended substantially uniform polymeric mixture may becalendered into sheets or films or may be processed to produce otherstructural shapes or forms depending upon the desired and use for thepolymer blend.

The polymer blend for the present invention may have added thereto,thermal stabilizers, fillers, dyes, lubricants, antioxidants, and otheradditives customarily employed to impart certain desired characteristicsto the finished product.

The blend of polystyrene with vinyl chloride-ethylene copolymer may beused to fabricate molded parts such as cams, gears, pipe fittings,bobbins, and spools. The blends may also find use in vacuum forming suchparts as refrigerator door liners, business machine housings, and toteboxes. Thin gauge sheet may be used for wall tile and letters for signs.

The blends of polypropylene with vinyl chloride-ethylene copolymer maybe used to prepare wrapping films, pipe, and bottles. The blend isparticularly suited for preparing containers such as bottles or foodpackages which may be immersed in boiling water without damage. Theblend is also suitable for insulating electrical wiring.

The blend of polyethylene and vinyl chloride-ethylene copolymer findsuse in preparation of films, coating of electrical wiring, manufactureof squeeze bottles, boxes, pails, pans, pitchers, refrigerator dishes,and pipe.

The rubber blends with vinyl chloride-ethylene copolymer (SBR, Butylrubber and EPR) find use in a wide variety of applications. They arearticularly suitable as substitutes for the more expensive neoprenerubber. Specific uses include hoses, gaskets, vibration dampingstructures, metal cable sheathing, and electrical cable sheathing. Therubber blends also are suitable for use in manufacture of clothing suchas booth, gloves, aprons, hoods, and rain wear.

The polystyrene blends and the rubber blends of the present inventionmay also be used to prepare foamed structures. Both rigid and flexiblefoams may be prepared from these blends by selecting both the amount ofvinyl chloride-ethylene copolymer incorporated in the blend and theamount of ethylene incorporated in the vinyl chloride-ethylenecopolymer.

The following examples provide illustrations of some of the preferredembodiments of the present invention. The examples are merely exemplaryand are not intended to limit the scope of the present invention. Allparts are by weight.

EXAMPLE I A mixture of 100 parts polystyrene and 11 parts of a vinylchloride-ethylene copolymer containing weight percent ethylene washeated and worked on a roll mill for 10 minutes to form a compatibleblend. The sheet was stripped from the roll mill and test samples cuttherefrom. The samples exhibited a notched Izod impact strength 4 (ASTMD-256) of 0.22 foot pounds. A sample of the blend had a heat distortiontemperature (ASTM D-648, 264 p.s.i. stress) of 78 C.

EXAMPLE II A mixture of 100 parts polystyrene and 60 parts of a vinylchloride-ethylene copolymer containing about 20 weight percent ethylenewas heated and worked on a roll mill for 10 minutes to form a compatibleblend. The blend was stripped from the mill and examined fortransparency and strength. The sheet was completely transparent and hadan extremely high strength with a high degree of toughness. The sheetmaterial was found to be self-extinguishing i.e., the material did burnin air only when heated by an open flame. In contrast, the polystyrenewithout the copolymer readily supported combustion.

EXAMPLE III A mixture of 100 parts of SBR rubber (a styrene-butadienecopolymer) and 60 parts of a vinyl chloride-ethylene copolymer whichcontained 80 percent vinyl chloride was blended by heating and workingon a roll mill. The sheet was stripped from the mill roll and examinedand found to be extremely strong, tough and elastic. The materialexhibited excellent oil resistance and was found to beselfextinguishing. The SBR rubber before blending had very poor oilresistance and readily supported combustion. 1

EXAMPLE 1V Example In was repeated using a butyl rubber instead of SBRwith substantially the same results.

EXAMPLE V A mixture of parts of polyethylene and 11 parts of a vinylchloride-ethylene copolymer containing 80 parts of ethylene was blendedby heating and working on a roll mill. The sheet was stripped from theroll mill and found to be very strong and highly elastic. Samples cutfrom the sheet exhibited an ultimate tensile strength (ASTM D-412) of1120 p.s.i. Another sample was tested and found to have an ultimateelongation of 420 percent. A sample of the polyethylene before blendingexhibited a lower ultimate tensile strength and a lower ultimateelongation.

EXAMPLE VI A mixture of 100 parts of polyethylene and 60 parts of vinylchloride-ethylene copolymer containing 80 per cent vinyl chloride wereblended on a roll mill by heating and working. The sheet was strippedfrom the roll mill and examined and found to be very tough and strong.The material was found to be self-extinguishing. The un blendedpolyethylene was not nearly as tough and strong and also readilysupported combustion.

EXAMPLE VII Example VI was repeated using polypropylene instead ofpolyethylene with substantially the same results.

The polystyrene used in preparing the blends with vinylchloride-ethylene copolymer may be selected from any of the commerciallyavailable solid polystyrene molding powders, such as those marketedunder the trade name Styron by Dow Chemical Company, Lustrex by MonsantoCompany, or the P series of polystyrenes made by Koppers Company. Bothso-called low-impact and high-impact polystyrene solids may be used inpreparing the blends of the present invention.

Suitable SBR rubbers are those produced according to standardizedprocedures for making GRfiS, S40, X-503 and other styrene-butadienerubbers. Commercial styrenebutadiene rubbers sold under the trade namesChemigum, Hycar OS, Butapene S, Nubum, Philprene, Polysor S, and Kryleneare eminently suitable for preparing the blends of the presentinvention.

Butyl rubbers (isobutylene-isoprene rubber) suitable for use inpreparing the blends of the present invention may be any of thecommercially available Butyl rubbers, such as the Polysor Butyl made byPolymer Corporation. Other Butyl rubbers made by the Standard CR-1formulae of the US. Rubber Reserve are suitable.

Any of the commercial solid polyethylenes are suitable for use inpreparing the blends of the present invention. The polyethylene may beeither the high density (Phillips, Ziegler or I.C.I.) type or the lowdensity (high pressure) type.

Polypropylene suitable for use in preparing the blends of the presentinvention may be any of the commercially available solid molding powderpolypropylenes, e.g. Profax polypropylene.

The nature of the foregoing polymeric materials suitable for use inmixing with vinyl chloride-ethylene copolymers to prepare asubstantially homogeneous blend are well known to those skilled in theart. Further details as to the physical and chemical properties of thesepolymers and methods for their preparation may be found in the followingtexts: Vinyl and Related Polymers, Calvin E. Schnildknecht, John Wileyand Sons, 1952 Edition; Polyethylene, R. A. V. Raff and J. B. Allison,Interscience Publishers, Inc., 1956; Polymeric Materials, Charles C.Winding and Gordon D. Hiatt, McGraw-Hill Book Company, Inc., 1961; andPolymers and Resins, Their Chemistry and Chemical Engineering, BrageGolding, D. Von Nostrand Company, Inc., 1959.

What is claimed is:

1. A blend of polymeric material comprising a physical mixture of (a) avinyl chloride-ethylene copolymer containing from about to about 80percent weight ethylene, and (b) polystyrene, said vinylchloride-ethylene copolymer being prepared by the copolymerization ofvinyl chloride and ethylene monomers.

2. A blend of polymeric material comprising a physical mixture 01 (a) avinyl chloride'ethylene copolymer containing from about 10 to aboutpercent weight ethylene, and (b) a styrene-butadiene copolymer rubbersaid vinyl chloride-ethylene copolymer being prepared by thecopolymerization of vinyl chloride and ethylene mono mers.

3. A blend of polymeric material comprising a physical mixture of (a)from about 5 to about 200 parts of a vinyl chloride ethylene copolymercontaining from about 10 to about 80 percent weight ethylene, and (b)about parts of polystyrene, said vinyl chloride-ethylene copolymer beingprepared by the copolymerization of vinyl chloride and ethylenemonomers.

4. A blend of polymeric material comprising a physical mixture of (a)from about 5 to about 200 parts of a vinyl chloride-ethylene copolymercontaining from about 10 to about 80 percent weight ethylene, and (b)about 100 parts of a styrene-butadiene copolymer rubber, said vinylchloride-ethylene copolymer being prepared by the copolymerization ofvinyl chloride and ethylene monomers.

References Cited UNITED STATES PATENTS 2,844,573 7/1958 Gluesenkamp eta1. 260897 2,919,252 12/1959 Canterino 260-889 3,014,887 12/1961 Howard2604 3,227,781 l/1966 Klug et al 260897 3,248,375 4/1966 Erbaugh 26087.53,390,208 6/1968 Montgomery 260-897 MURRAY TILLMAN, Primary Examiner M.I. TULLY, Assistant Examiner US. or X11, 2s0 2.s, 87,5, 3 97

